Various fuel gases such as natural gas, hydrogen, acetylene, and methane, can be stored in a pressurized gas storage tank. To increase storage density and to reduce total system weight, high working gas pressure and light weight tank design are required. For pressurized hydrogen gas storage, special attention must be paid to tank design and material selection due to high permeability of hydrogen through most materials and well-know hydrogen embrittlement of many common metals. Furthermore, the ignition potential of hydrogen is much greater than methane. Theoretically, hydrogen permeation is approximately 34 times greater than that of methane. Permeation and leakage are recognized as major issues. The pressure in a compressed hydrogen fuel tank for vehicle fuel cells can be as high as 700 bar (˜70 Mega-Pascal). The tank connector components, such as boss-liner interface connector and O-rings, must be carefully engineered and assembled in order to prevent leaks. Any minor defects or mis-assembly of those connectors can result in significant gas leakage.
The stored hydrogen gas is typically discharged from the tank through a pipe. At least one pressure regulator is provided that reduces the pressure of the hydrogen within the tank to a suitable pressure for feeding into a fuel cell system. As the hydrogen is discharged from the compressed tank, the pressure of the stored hydrogen in the tank will decrease and the tank temperature will fall. If the flow rate of the hydrogen discharged from the tank is high enough and/or the temperature of the environment is low enough, the temperature in the tank can reach as low as −80° C. On the other hand, when the tank is being charged with hydrogen, the temperature of the hydrogen in the tank can rise up to 85° C. due to the compression of the hydrogen inside the tank. Such a wide temperature swing between −80° C. and 85° C. in repeated charging/discharging cycles puts significant mechanical stresses on tank connector components, including O-rings and other sealing adhesives. Under such operating conditions, the o-rings and sealing adhesives may deteriorate and possibly be damaged, resulting in hydrogen leakage. Therefore, there is a need for improved sealing material and tank design that are more resistant to the cyclic stresses and offer desirable self-sealing characteristic.